The present invention relates to valves used to control the flow of fluids under pressure and, particularly, to modifying valves in order to make them suitable for use with fluids under higher pressures than the unmodified valve was suitable for use.
Valve bonnets may be bolted onto the valve body structure or valve housing. Often times such bonnet-housing connections rely upon only a gasket placed between the housing and bonnet to maintain a fluid-tight seal. This is especially true for gate valves where the pressure rating of the valve is generally limited by the integrity of the seal made between the valve bonnet and the valve housing. Thus, for example, the seal between the valve bonnet and housing may leak fluid at a pressure above 600 psi even though structurally the valve is suitable for use with fluids at pressures as great as 1000 psi.
It would, therefore, be desirable to have a method of mounting the valve bonnet on the valve housing which would result in a seal that would allow the valve to be used at higher pressures than when the valve is bolted onto the valve body using a gasket to maintain a seal.